Methods of the type just described are advantageous, above all, when the pieces to be bent are of relatively small size. In that case, in fact, the plan developments of several such pieces can be defined on a single metal sheet. The part of the sheet that surrounds the plan developments of the various pieces normally constitutes a waste but, before this material is thrown away, it is used as a kind of stiffener or stiffening frame that sustains the individual pieces during the bending operation. On completion of the bending operations, the bent pieces are separated from the stiffening frame by either cutting or breaking the microjoints.
A method for cutting and bending pieces of sheet metal in accordance with the steps just described in broad outline can be realized, for example, in an integrated cutting and bending system of the type described in Italian patent application No. TO95A00059 filed by the present applicant. In a system of this type the bending can be carried out in automatic fashion by means of the particular type of press described in EP-A-0725692. For the bending operations to be correctly performed in a system of this type, it is essential to employ bending tools (i.e. punch and die) of a length substantially the same as the length of the bend to be made. This implies the need not only of keeping a considerable stock of tools with a large number of spares, but also of frequently changing the tools used with the bending press whenever the bends to be made are of different lengths.